1. Field of the Invention
The present invention relates to IEEE 802.11 wireless local area networks (WLANs). More particularly, the present invention relates to estimating radio frequency (RF) interference and determining the optimal channel or channels for use by an access point (AP) in an IEEE 802.11 WLAN.
2. Prior Art
IEEE 802.11 (Wi-Fi) wireless networks have grown in popularity in recent years and are found in business, industry and the home. Wi-Fi networks operate in the 2.4 GHz Industry, Scientific, and Medical (ISM) and 5 GHz Unlicensed National Information Infrastructure (U-NII) public bands that are unlicensed by the FCC. Many wireless devices compete for usage time in the public bands, and these devices transmit RF energy that introduce interference. The performance of WLANs that employ 802.11 network adapters are sensitive to interfering RF transmissions from other wireless sources, both 802.11 and non-802.11, which negatively impacts the performance of a wireless network.
An Access Point is an 802.11 device that serves as the central hub for a wireless network through which a station accesses a network. When an access point is installed and configured one chooses one of 11 (802.11b/g) or 12 (802.11a) Wi-Fi channels in which the access point will operate. The channel chosen can have a big impact on how well the network performs because of active and latent RF interference in the environment of the AP.
When installing a wireless network or troubleshooting one that performs poorly it is important to select a channel that is not subject to RF interference from other devices. With wireless systems it is difficult to predict the propagation of radio waves and to detect the presence of interfering signals without the use of test equipment. Typically an RF spectrum analyzer is the preferred tool for detecting and identifying sources of interference and for providing information that allows optimal configuration of a Wi-Fi network. There are also commercial devices designed to measure RF interference.
In general, their short-comings fall under two categories—either they do not employ an 802.11 device for measuring the effect of RF interference or they require multiple devices—e.g. an access point (AP) and wireless stations (STAB) —that are specially programmed to implement a custom protocol.
The WifiSleuth 2.4 GHz WiFi Analyzer (http://www.nutsaboutnets.com/performance-wifi/products/product-wifisleuth-wifi-spectrum-analyzer.htm) is developed and sold by Nuts About Nets, LLC, which is this inventor's company. This product is a 2.4 GHz spectrum analyzer that presents channel-centric views of RF data. It is not an 802.11 device and, therefore, may not truly reflect how 802.11 channels will perform in the particular environment where the measurements were taken.
Available 802.11 discovery tools such as NetStumbler (http://www.netstumbler.com/ and http://www.netstumbler.org/) and Wi-Fi scanners and locators do not give an accurate picture of channel performance because they do not see non-802.11 traffic. Also, though they can detect the presence of an 802.11 access point that is using a particular channel, they only report beacon strength and do not provide information related to channel performance, that is, how efficiently an RF energy packet with a digital payload will transmit in that channel. As a result they too (as with RF spectrum analyzers) are not reliable diagnostic tools for estimating channel performance or determining the optimal channel to be used for an AP. U.S. Pat. No. 6,985,465 issued to Gerard G Cervello, et al describes a method and system for selecting a IEEE 802.11 WLAN channel between an AP and a plurality of stations (STAB). This invention requires multiple 802.11 devices (i.e. at least one AP and several STAB) that are specially programmed to implement a custom protocol for negotiating and selecting which channel(s) to use.
U.S. Pat. No. 7,158,759 issued to Hansen, et al describes an AP that measures interference. When a threshold is exceeded it initiates an exchange with the STAB and negotiates a better channel to use. This invention also requires multiple 802.11 devices (i.e. at least one AP and several STAB) that are specially programmed to implement a custom protocol for negotiating and selecting which channel(s) to use.
U.S. Pat. No. 1,822,218 issued to Hongbing Gan describes an approach for selecting sets of channels that involves determining the performance of the channels. The participant identifies the selected set of channels and provides that data to other participants of the communications network who then communicate over the set of channels by using a frequency hopping protocol. This invention requires multiple 802.11 devices (i.e. at least one AP and several STAB) that are specially programmed to implement a custom protocol for negotiating and selecting which channel(s) to use. U.S. Pat. No. 7,110,322 Issued to Richa Malhotra, et al describes an algorithm for the assignment of channels used by APs in wireless LANs in a dynamic way to achieve the best performance. The assignment of channels is based on a procedure in which an AP is passively listening on the other channels during idle time and calculates the channel with the least interference and sharing. If the AP experiences too much disturbance on the channel it is using, it will decide to switch to the calculated optimal channel. This invention requires a specially programmed access point.
The primary object of the invention is to present a single device for use with a general purpose computer that can measure efficiency of transmission of energy packets in the various available RF channels for the ultimate purpose of selecting one or more channels for use by an AP.